When fields are declared protected, there is the possibility that methods in subclasses will directly access them, effectively increasing the coupling within a class hierarchy.

将字段声明为受保护时，子类中的方法就有可能直接访问它们，这样就可能有效地增加类层次结构中的耦合。

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This approach makes testing protected methods much easier because the test case class can now extend the class that contains the protected methods.

这种方法使得测试受保护的方法非常容易，因为测试案例类现在可以扩展包含受保护方法的类了。

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Sometimes you need to write a subclass (often as an inner class) in order to test protected methods.

有时需要编写一个子类（通常作为内部类）来测试 protected 的方法。

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